1. Field of the Invention
The present invention relates to a label sheet positioning device of a barcode printer, and in particular to a label sheet positioning device that is applicable to a barcode printer to provide inclining of a printing head holder and a printing head for close engagement with a label sheet by means of a universal fine adjustment mechanism.
2. The Related Arts
A conventional barcode printer contains a label sheet which is contained inside the barcode printer for printing thereon barcodes by the operation of a printing mechanism and then out-fed. To control the printing precision of the label sheet, a mechanism for regulation upper and lower side pressures must be provided in the barcode printer for the label sheet to ensure closeness or tightness between the label sheet and the printing head. FIG. 1 of the attached drawings shows a conventional pressure regulation mechanism 1A of a barcode printer 1, which includes two pressure adjusting knobs 2, 3 that effect direct downward depression for adjusting the tightness of engagement and pressure of a printing head 4 that is located below the pressure regulation mechanism 1A with respect to a label sheet 5 and thereby adjusting printing quality of the printing head 4 applying to the label sheet 5.
In the structure of the pressure regulation mechanism 1A of the barcode printer 1 shown in FIG. 1, when the width of the label sheet 5 is identical to or close to the distance between the two pressure adjusting knobs 2, 3, the adjustment of the pressure and tightness between the label sheet 5 and the printing head 4 can be properly done. However, for a label sheet 5 having a reduced width, such as a small-size label sheet 5 having only a quarter of the original sheet width, it is no longer possible to effect proper pressure adjustment for ensuring tight or close engagement between the printing head 4 and the label sheet 5 by simply operating the two pressure adjusting knobs 2, 3 of the pressure regulation mechanism 1A with respect to the label sheet 5. Very likely, an unbalance of pressure may occur, causing inclination at one end between the label sheet 5 and printing head 4, and thus making the printing result on the label sheet 5 unclear or leading to deterioration of printing quality.
Further, if different designs of the pressure regulation mechanism 1A and the pressure adjusting knobs 2, 3 are given for different widths of the label sheet 5, then the manufacturing costs are increased. Further, in case that the inclination between the label sheet 5 and the printing head 4 is toward the front-rear direction, or other directions rather than the left-right direction, then the conventional structures of the pressure regulation mechanism 1A and the pressure adjusting knobs 2, 3 cannot ensure tight or close engagement between the label sheet 5 and the printing head 4 and proper printing on the label sheet 5. This makes the conventional barcode printer 1 adverse to the development of the industry.